Basic Operational Amplifier Functions

The operational amplifier is basically a differential amplifier with two inputs, one inverting and the other non-inverting. Any signal applied to the inverting input will appear at the output in an amplified inverted form. Similarly, any signal applied to the non-inverting input will appear at the output as an amplified form of the input. Signals applied to both inputs will add or subtract accordingly at the output giving true differential amplification. Identical inputs to both input terminals should, if correctly set up, produce zero output. Figure 7.1 illustrates this simple application of the operational amplifier using d.c. and a.c. signals which are applied as V₁ and V₂ to produce V_OUT. The remainder of this chapter demonstrates many other simple applications of the basic operational amplifier as a prelude to the working circuits of chapter 8.